The invention relates to determining the position of an object having faces and edges, in particular a sheet pile, having at least one light-sensitive receiver and an evaluation device.
A method, a device and a positioning system determining the position of an object having faces and edges, is shown, for example, in DE 198 16 181 A1. What is involved is the positioning of a sheet pile for feeding sheets to a sheet-fed printing press. Proposed for this purpose are spacing sensors which in each case determine at only one point the spacing of the sheet pile from a reference point. Further proposals in this publication consist in using a CCD linear array to determine the jump in intensity caused by a side edge of a pile, or detecting the contour of a side edge of a pile by a camera and using this information to position the sheet pile. A disadvantage of these proposed determinations of the position of the sheet pile is that the sensor can be used to determine no more than one spacing measure, resulting in the need to arrange a multiplicity of sensor to position the sheet pile accurately. This would require two sensors just to detect the angle of deviation of a line, for example an edge, assuming that the deviation of the actual position from the desired position occurs in a plane and not in a three-dimensional space. However, since the deviations occur in such a space, and measure and angular deviations as well as oblique or corrugated front edges, possibly even paper stacks rotated above the vertical axis can occur, it is necessary according to the known prior art either to operate with a high outlay or to dispense with detecting all possible errors. Of course, this problem is not limited to the positioning of a sheet pile, but concerns the determination of the position and thus also the positioning of all sorts of objects which have faces and edges which can be used to determine the position. Moreover, the same problem arises when determining the shape of an object, such as the height of a paper stack, or when detecting and correcting deviations such as an oblique or rotated outer surface of a pile.
It is therefore the object of the invention to simplify the determination of the position, and thus also the positioning of an object having faces and edges, in particular a sheet pile.
The object is achieved according to the invention by virtue of the fact that at least one defined illumination zone is produced on the object by diverging beams, and in that at least two boundaries of at least one illumination zone are detected and used to determine the position of the object.
Further, the object is achieved according to the invention by virtue of the fact that at least one illumination system is configured for producing at least one boundary, and in that the at least one receiver detects at least two boundaries and transmits them to the evaluation device for the purpose of determining the position of the object.
In order to configure the positioning t provides for fitting it with the abovementioned device and with a controller which uses the determined actual position of the object to cause control movements of the positioning system in order to bring the object into a desired position.
The advantage of the invention consists in that two spacings from a reference line can be detected as early as when detecting two boundaries of an illumination zonexe2x80x94this is the simplest configuration of the invention. If the detection of edges of the object and/or further boundaries of the illumination zone or further illumination zones on one or more faces of the object is also included, the position of an object, in particular its position in space, can be detected with relatively few receivers. It is also possible in this way to detect the shape of an object, in particular it is possible to detect oblique positions or corrugations of an outer edge of a sheet pile, or a vertical rotation of a sheet pile about an axis. Above all, it is possible to retain a relatively high number of measured values using a receiver of planar design For example, by including two edges of a face it is possible to position it completely, including its angular position in spacexe2x80x94that is to say within an x, y and z-coordinate system. It is possible with the aid of three planar receivers to determine not only the positioning of a cuboid in space, including the angular position, but additionally also to detect irregularities in the cuboid, for example the oblique position or the rotation of a sheet pile.
In order to detect complicated objects, for example the corrugation and rotation of the face of a sheet pile, it is possible to produce a multiplicity of illumination zones on a face and to detect these with the aid of a planar receiver. Of course, it is possible to fit such receivers on a few or all sides of a body in order to be able to detect virtually any desired body having faces and edges.
A few expedient embodiments may be mentioned from the multiplicity of possibilities. In this case, the device for carrying out the method can be produced from commercially available optoelectronic components, and so the overall device can be provided cost-effectively and will function reliably and free of maintenance over a long period.
An expedient refinement of the method provides that the illumination zone extends as far as an edge of the object in order to determine the position of the edge and the position of the face adjoining this edge. It is possible in this way to determine both the position of the face relative to a reference line, and the position of the edge. However, the position of this edge also provides the position of the face adjoining the first face at this edge, and it is possible in this way to determine the spacing in two orthogonal directions. With reference to the device, at least one illumination system is directed onto the object in such a way that at least one edge of the object forms at least one boundary of at least one illumination zone. In this case, a receiver can detect, for example, the edge and the boundary of the illumination zone on the face, and it is thereby possible to measure the two above-named spacings and correct them by a position system.
A further refinement of the method provides that at least one further illumination zone produced on a face id detected in order to determine the position of the face. In this case, it is possible not only to determine the distance of the face from a reference line or from a reference surface, but also the angular position of the face with reference to the reference line or a reference surface. With reference to the device, it is then necessary to provide at least one illumination system for producing at least one further illumination zone, and to provide the receiver to detect this at least one further illumination zone. In order to determine the angular position with reference to a line, it suffices to detect boundaries of the illumination zones which are aligned in parallel. If, by contrast, the position of a face of the object is to be determined in space, it is necessary to detect at least two further boundaries which run at an angle to at least two boundaries, which are likewise detected. It is expedient to detect boundaries which are in mutually orthogonal alignment, at least one illumination system being provided with reference to the device in such a way that it produces at least one illumination zone with boundaries which run at least partially at an angle to one another, preferably being aligned in a mutually orthogonal fashion. In order to be able to detect these boundaries by a receiver, it is expediently provided that at least one receiver is in a planar fashion to detect a plurality of boundaries, lying in a face, of at least one illumination zone. It is possible in this way to detect the position of a face in space, including its angular position and also its boundaries. It is even possible to determine deviations of the face from planarity such as, for example, corrugated deformations.
By detecting further boundaries on further faces of the object, it is possible to determine its position in space. It is, moreover, possible even to detect the size and shape of the object. For this purpose, it is provided with reference to the device that at least one further illumination system and at least one further receiver are arranged for the purpose of detecting boundaries of illumination zones on further faces of the object.
Planar receivers, for example CCD arrays, detect any type of boundaries of illumination zones on a face. With reference to detecting sheet piles, this has the advantage that the course of the pile sides and front edge can be detected at least in a subregion. It is also possible to determine the upper horizontally running pile edge, and thus the pile height. It is also possible with the aid of such planar elements to measure all three coordinates, these being in the case of a sheet pile, for example, the pile height and the lateral alignment, which can be detected, for example, from the upper half of a planar element. The lower half of the planar element can then be used for the triangulation of the remaining dimensions, and can serve the purpose of bringing the front face of the pile into its desired position.
Pulsed light, expediently infrared light, is preferably used as the light. The device then provides a pulsed light source, preferably an infrared light source and corresponding receivers. The advantage of this is that a high degree of suppression of unwanted light is achieved, it thereby being possible to illustrate the jumps in intensity, which specify the boundaries of the illumination zones, with as much contrast as possible on the receiver.
The positioning system can, of course, be for positioning all types of detected objects. A significant field of application is the positioning of a paper stack for automatically feeding paper sheets to a printing machine. The positioning system is then such that the front face, a side edge and the front upper edge of the paper stack are detected and the position is corrected in such a way that these assume their desired position. A particularly advantageous development of the positioning system provides that the latter is such that, given irregularities in the front face or in a side edge of the paper stack, it undertakes continuous correction of the paper stack to achieve the desire position for the uppermost paper sheet. This is important because the uppermost paper sheets are to be fed to the printing machine by a sheet guide, and it is necessary to align these sheets exactly.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.